November 28, 2012

Seasons Change On Saturn’s Titan Moon

To every thing there is a season, and a time to every purpose under the heaven. While the Book of Ecclesiastes and American folk singer Pete Seeger may not have considered Titan, the planet Saturn´s largest moon, as something unto which there is a season, it does seem that the moon has seen a type of turn or change in the seasons.

On Wednesday, scientists using the international Cassini spacecraft have studied the rapid change in seasons on the moon, following its equinox in August 2009. It was then that the formation of a swirling vortex and build up of exotic gases at unexpectedly high altitudes was observed.

This change of seasons is notable, as Titan is the only other body in the solar system with a thick nitrogen-rich atmosphere that is similar to that of Earth´s. However, Titan´s unique atmosphere also contains methane and hydrogen, with trace amounts of other gases that include hydrocarbons, which form at high altitudes as a result of reactions with sunlight.

The data from NASA´s Cassini spacecraft reportedly tie a shift in seasonal sunlight to what is now being described as a wholesale reversal. At the south pole, the data presents clear evidence for sinking air where it was upwelling earlier in the mission.

The key to circulation in the atmosphere of the moon is reportedly a certain slant of light. The findings from this were data were published in the journal Nature.

“Cassini's up-close observations are likely the only ones we'll have in our lifetime of a transition like this in action," said Nick Teanby, the study´s lead author based at the University of Bristol, England, and a Cassini team associate said in a statement. “It's extremely exciting to see such rapid changes on a body that usually changes so slowly and has a ℠year´ that is the equivalent of nearly 30 Earth years.”

According to the data, there has been up to a hundred-fold increase in atmospheric gas concentration, which was measured over the south pole at the same high altitudes. Cassini´s instruments found these gas molecules were sinking through the atmosphere at a rate of 1-2 millimeters per second.

Cassini further detected complex chemical production in the atmosphere at up to 400 miles (600 kilometers) above the surface, which revealed the atmospheric circulation extends about 50 miles, or 100 kilometers, higher than previously expected. These results further suggest to researchers there is a detached layer of haze, something first detected by NASA´s Voyager spacecraft, and perhaps not so detached after all. This is because complex chemistry and vertical atmospheric movement is occurring above this layer, which may instead be the region where the small particles combine into larger, but more transparent, clumped aggregates that descend deeper into the moon´s atmosphere. It could be this that in fact gives Titan its characteristic orange appearance.

“Next, we would expect to see the vortex over the south pole build up,” said Mike Flasar, the CIRS principal investigator at NASA´s Goddard Space Flight Center in Greenbelt, Md. in a statement. “As that happens, one question is whether the south winter pole will be the identical twin of the north winter pole, or will it have a distinct personality? The most important thing is to be able to keep watching as these changes happen.”

Cassini will continue to observe how the seasons on Titan develop, and Dr. Conor Nixon at NASA Goddard Space Flight Center suggested, “These results are giving us the first detailed look at changes occurring in Titan´s atmosphere around the time of equinox, a season which has not been viewed up close by a spacecraft previously. This shows the really great science that is coming out of the Cassini extended mission phases since 2008, and we look forward to seeing the further changes that will occur over the next five years until the end of mission in 2017.”

To every thing there is a season, and apparently that includes the moon of Titan.